Hydrocarbon lead production



United States Patent 3,431,185 HYDROCARBON LEAD PRODUCTION Gene C.Robinson, Baton Rouge, La., assignor to Ethyl Corporation, New York,N.Y., a corporation of Virginia No Drawing. Filed June 22, 1964, Ser.No. 377,097 US. Cl. 204-59 2 Claims Int. Cl. Btllir 1/00 ABSTRACT OF THEDISCLOSURE This application relates to a mixture of tetraorganoleadcompounds and an electrolytic process for the production of the mixtureby electrolyzing a liquid composition comprising a vinylic Grignardreagent and an alkyl halide.

The preparation of vinyl lead compounds containing at least one alkylradical has been disclosed in U.S. Patent 3,071,607, patented Jan. 1,1963. According to this patent the mixed lead compounds may be producedfor example by reacting a vinyl Grignard reagent with the appropriatelead salt. However, such a process has certain disadvantages such as therelatively low yields obtained and the high cost of the required leadsalt. It is accordingly an object of this invention to provide animproved process for the production of lead compounds having bothvinylic and alkyl radicals attached to the lead. It is a further objectof this invention to directly produce an organolead composition suitablefor improved antiknock compositions. Another object is to produceorganolead compounds having both alkyl and vinylic groups attached tothe lead at higher yields and efiiciencies. These and other objects willbe apparent in the description which follows.

According to this invention lead compounds having both vinylic and alkylgroups attached to the lead may be produced at high yields and currentefficiencies by electrolyzing in an electrolytic cell having a leadanode, a liquid composition comprising a vinylic Grignard reagent (i.e.,a vinylic magnesium halide) dissolved in an alkyl halide. By vinylicGrignard is meant compounds of the formula R C=CHMgX wherein R isselected from the group consisting of H, CH CH CH and mixtures thereofand X is a halogen. The alkyl halides have the formula R'Y wherein R isa lower alkyl radical and Y is a halogen. The anode of the electrolyticcell supplies the lead of the organolead product. The cathode may beeither lead or another suitable material such as stainless steel.

One of the unexpected advantages of this invention is that a desireddistribution of tetraorganolead compounds comprising tetraalkyl lead,trialkylvinylic lead, dialkyldivinyliclead, alkyltrivinylic lead andtetravinylic lead is achieved. Such compositions have been found to beof particular advantage as an antiknock composition in gasoline.Furthermore, by producing these mixed compositions directly, the processof redistributing the organo radicals in a mixture of tetraalkyl leadand tetravinylic lead compounds is avoided.

A further advantage of this invention is that the alkylvinylic compoundsare produced in high yields in an eflicient process. It has been foundthat the lead compounds may be produced at current efiiciencies ofgreater than 100 percent. Thus considerable saving in currentexpenditures is realized and a greater throughput per unit time isachieved. These excellent results were particularly surprising becausewhen a composition of vinyl Grignard reagent and vinyl chloride waselectrolyzed only a very low yield of organolead compound was produced.The yields may be considerably higher using the process of thisinvention, wherein a composition comprisng a vinylic Grignard reagentand an alkyl halide is employed, than when a composition of alkylGrignard and vinylic chloride is employed in the electrolytic cell. Thereasons for these considerably improved results are not understood.

It is one of the features of this invention that the liquid compositioncomprising the vinylic Grignard reagent and the alkyl halide has a highconductivity. It is possible to conduct the reaction in the absence ofadded electrolytes. By conducting the reaction in the absence ofadditional electrolytes or solvents the recovery of the organleadproduct as well as the by-products is facilitated.

The process of this invention may be more completely understood andillustrated -by the following examples. All parts are by weight unlessexpressed otherwise.

Example I The electrolytic cell used in these tests has a 29 mm. by 200mm. Pyrex test tube fitted with a stopper having a -inch glass T forcharging the electrolyte or for connection to a gas bure'tte fitted withmercury for collecting and measuring gases evolved. When gas was notbeing collected the side arm of the glass T was connected to a nitrogenbubbler for maintaining an inert atmosphere in the cell. A hypodermicneedle through the stopper was connected to a small cylinder forsupplying the alkyl halide to the electrolytic solution. Two copperwires for the electrical leads were fitted tightly through holes in thestopper. The cathode was a stainless steel rectangular sheet which wasabout 2 cm. wide, 10' cm. long and about -inch thick. The cathode wassandwiched between two lead anode sheets of approximately the same sizeas the cathode. Teflon spacers held the electrodes about 0.5 cm. apart.Electrical direct current (DC) was supplied for the test by a batterycharger operating off regular 115 volt AC supply line and voltagecontrol was obtained by a rheostat on the battery charger. The currentwas measured by an ammeter and by a copper coulometer.

Vinyl magnesium chloride was prepared by the reaction of magnesium andvinyl chloride. Magnesium chips, 121.6 g., were reacted in 1,075 g. oftetrahydrofuran with 396 g. of vinyl chloride. The reaction product wascooled and unreacted vinyl chloride was vented. The product solution,1300 ml., was decanted and 500 m1. of tetrahydrofuran was added toextract the residue. Most of the residue went into solution, which wasthen decanted and added to the product solution giving it a total of1900 m1. Aliquots of this product solution indicated it was 2.64 molarwith respect to magnesium and 2.74 molar with respect to chloride ions.The product solution (25 ml. portions equivalent to 67.25 millimols ofvinyl magnesium chloride) was used in the electrolyte solution for theelectrolysis test.

A mixture of tetravinyl lead, trim-ethylvinyl lead, dimethyldivinyllead, methyltrivinyl lead, and tetramethyl lead was produced in theelectrolytic cell. The vinyl magnesium chloride prepared above in anamount of 67.25 millimols was combined with 10 ml. of dibutyl Carbitol(diethylene glycol dibutyl ether) and 15 ml. of benzene to constitutethe electrolytic solution. Methyl chloride, 25 g., was added duringelectrolysis. The cell was cooled by a flow of tap water around thecell. The run was 2.5 hours long. The initial current Was 200 milliampsand the voltage was maintained at 5.3. During the run the current wasallowed to drop to a minimum of milliamps while the voltage was heldconstant at 5.3. The product contained a total of 1.27 g. of leadpresent as a mixture of tetraorga-nolead compounds. This productcomprised a desired mixture of trimethylvinyl lead, dimethyldivinyl leadand methyltrivinyl lead together with some tetrametyl lead andtetravinyl lead. No triorgano lead compounds were detected. The productwas analyzed by the dithizone method of analysis. Only a negligibleamount of gas was produced during the run. The current efficiency duringthe run was 178 percent.

Example II The procedure of Example I is repeated with the exceptionthat ethyl chloride was substituted for the methyl chloride of ExampleI. A high yield of product comprising triethylvinyl lead, diethyldivinyllead, and ethyltrivinyl lead, together with a small amount of tetraethyllead and tetravinyl lead is obtained. In this example negligible gas isproduced and the current efficiency is high.

Example III To illustrate the advantage of the instant invention wherebythe electrolytic solution comprises a vinylic Grignard reagent and analkly halide, a comparative run was made wherein vinyl chloride wassubstituted for the methyl chloride of Example I. The same vinylmagnesium chloride of Example I in an amount of 67.25 millimols wascombined with 45 g. of vinyl chloride and 25 ml. of dibutyl Carbitol toform the electrolytic solution. The nominal milliamps were 100 and thenominal voltage was 3 volts. The run was operated for a period of 18hours, yet only 0.040 g. of organolead compounds were produced. Duringthe run large amounts of gases were evolved.

Example IV To further illustrate the unexpected nature of thisinvention, Example III was repeated using 67.25 millimols of the vinylmagnesium chloride, 240 g. of vinyl chloride, ml. of dibutyl Carbitoland ml. of benzene. The nominal milliamps were 100 and the voltage was2.9. During a run of 17 hours only a relatively small amount of organolead compounds were produced. During this run also large amounts ofgases were evolved. When the voltage in this run was gradually increasedto 24 while maintaining a current flow of 100 milliamps, no significantimprovement in the results were noted.

As pointed out in the examples, when a composition comprising vinylmagnesium halide and vinyl chloride was electrolyzed very low yields oftetraorgano metallic compounds were obtained. It was accordinglysurprising that when an alkyl halide such as methyl chloride wassubstituted for vinyl chloride that high yields of the varioustetraorgano lead compounds were produced.

The alkylvinylic lead compositions produced according to the presentprocess comprise, in general, organolead compounds having between 1 to 3vinylic groups attached directly to lead and the remaining valences ofthe lead are satisfied by alkyl radicals. Generally the alkyl radicalswill contain from 1 to 8 carbon atoms, with the alkyl radicals havingone or two carbon atoms being particularly preferred. The alkyl or vinylgroups may be the same or different. The examples of compounds that maybe produced according to this invention are trimethylvinyl lead,dimethyldivinyl lead, methyltrivinyl lead, triethylvinyl lead,diethyldivinyl lead, ethyltrivinyl lead, methylethyldivinyl lead,methyldiethylvinyl lead, di-nbutyldivinyl lead, n-hexyltrivinyl lead,Z-ethylhexyltrivinyl lead, dimethylethylvinyl lead, dimethyldipropenyllead, dimethyldibutenyl lead, methyltriisobutenyl lead,isopropyltrivinyl lead, methyldivinylpropenyl lead, mixtures thereof andthe like.

Particularly preferred compositions produced are those containing themixed organo lead compositions such as one containing tetraalkyl lead,trialkylvinyl lead, dialkyldivinyl lead, alkyltrivinyl lead, andtetravinyl lead, wherein the alkyl groups contain from one to threecarbon atoms. Such compositions may be produced directly by the processof this invention. These compositions possess unique characteristicssuch as for antiknock compositions, and it is an important feature ofthis invention that these compositions may be produced directly withoutthe necessity of redistributing a combination of tetravinyl lead andtetraalkyl lead. A predominately alkylvinylic lead composition may beproduced.

One method for producing mixed lead compounds wherein the alkyl groupsare different is to utilize a combination of alkyl halides, such ascombination of methyl chloride and ethyl chloride. The methyl chlorideand ethyl chloride are then combined with the vinylic Grignard reagentto form the electrolytic composition. The mixture of alkyl halides maybe present in any combination and more than two alkyl halides may alsobe employed.

The vinylic Grignard agent of the formula R C CHMgX may be produced inconventional manner. Generally the halogen of the Grignard reagent aswell as for the alkyl halide will be selected from the group consistingof chlorine, bromine, iodine and mixtures thereof. Preferred halogensare chlorine and bromine with chlorine being particularly preferred.

The ratio of the alkyl halide to the vinylic magnesium halide present inthe electrolyte may be varied somewhat but generally will be in theratio of 0.1 to 10 mols of alkyl halide per mol of vinylic magnesiumhalide. A preferred ratio of alkyl halide to vinylic magnesium halide isbetween 0.75 and 2.0 mols of alkyl halide per mol of vinylic magnestiumhalide. The process may be operated as a batch process or may beoperated continuously. All of the vinylic magnesium halide and alkylhalide may be added initially or either of these may be addedcontinuously or intermittently throughout the reaction. Of course, in acontinuous operation the electrolyzed composition may be continuously orintermittently removed from the cell. Similarly, additional or new leadanodes may be added as required.

The cell employed may be of conventional design with one or moreelectrodes and cathodes. Provision should be made for the release of anygases evolved during the reaction. Also the cell should be suitable foroperating under the pressure generated by the particular reactants atthe temperature of reaction. Suitably the electrolytic solution will beanhydrous.

The temperature during electroylsis is not critical. It should besufiiciently high to give reasonable reaction rates but should not beabove the decomposition temperature of the organometallic reactants orthe organolead products. Thus, the operating temperature of the reactiondepends upon the particular organometallic compounds involved. Ingeneral, suitable temperatures are between about 30 C. and about 130 C.,but temperatures from about 15 to C. are preferred to facilitate heatremoval, for maximum current efficiency and for best results. Highertemperatures can be employed when using organolead thermal stabilizers.In some instances considerable exothermic heat is generated andconsequently a cooling medium may be desired to control the temperature.

About atmospheric pressure is normally employed, although subatmosphericpressures are permissible. In some instances, supraatmospheric pressureis preferred, particularly when employing a relatively high temperatureand a relatively volatile solvent or electrolyte. Also, a pressure ofinert gas is sometimes desirable, for example to assure anhydrousconditions. The pressure will generally be from about 0 to 500 p.s.i.with the range of about atmospheric (STP) to 259 p.s.i.g. beingparticularly suitable In some instances various solvents can be employedduring the electrolysis step. The solvent should desirably dissolve thevinylic Grignard reagent and the alkyl halide and preferably will beinert to reaction with the organolead product. The use of a solventhowever is not essential to the operation of the process and its absencemay be desirable in some instances. Thus when electrolyzing theelectrolyte in the absence of a solvent, the organo lead compound isgenerally insoluble and separates as a distinct phase which can easilybe recovered. When a solvent is employed, it is not necessary that theorgano lead product be soluble in the solvent. When the organo leadproduct is insoluble in the solvent system, it can be recovered directlyfrom the cell as a separate phase. In this case it is generallydesirable to Withdraw a part, of the solvent-containing electrolyte,either continuously or periodically, to use as a solvent for the freshelectrolyte feed. In general, solvents suitalble are the ethers andpolyethers (including cyclic ethers), tertiary amines, otherorganometallics, amides and substituted amides, and hydrocarbons,particularly the aro matic hydrocarbons. Typical examples of suitablesolvents are illustrated in the above examples. Similar results areobtained when these examples are repeated with triisopropyl amine,toluene, xylene, and the like. Additional typical examples of suitablesolvents are dialkylamides such as diethylamide and ethers, such asdimethyl ether, methylethyl ether, methyl-n-propyl ether, and mixturesof these. Suitable polyethers are ethylene glycol diethers, such asmethylethyl, diethyl, ethyl'butyl, and dibutyl; diethylene glycolethers, such as dimethyl, diethyl, ethylbutyl and butyl lauryl;trimetylene glycol ethers, such as dimethyl, methylethyl; glycerolethers, such as trimethyl, diethyl methyl, etc.; and cyclic ethers, suchas dioxane and tetrahydrofiuran. Typical amines suitable for thisinvention include aliphatic and aromatic amines and heterocyclicnitrogen compounds. The preferred tertiary amines for use in thisinvention are trimethyl amine, dimethyl ethyl amine, tetra/methylethylene diamine and n-methyl morpholine. Primary and secondary aminescan also he used, such as methyl amine, dimethyl amine, etc.

The lead anode can be pure lead or alloys thereof of varying shapes.Typical examples of alloy metals are tin, bismuth, cadmium, antimony andcopper. In some cases sodium, lithium, magnesium, and zinc are suitable.Likewise the lead or lead alloys can be coated or impregnated on aconductive metal, either metallic or non-metallic, such as graphite. Thecathode can be any suitable conductive metal but is preferably one whichdoes not alloy with the metal produced.

The voltage and amperage necessary for the reaction depend upon theparticular organo lead compound being formed, as well as upon thespecific resistance of the cell. In general, the potential across theelectrodes should be between about 0.5 and 50 volts, although notgreater than volts is normally required or desirable. Preferably, apotential of 1-1 5 volts is employed. In general, not greater than 0.25ampere/ sq. cm. is employed. A preferred range is between 0.002 to 0.1ampere/ sq. cm.

Alkyl vinylic lead compounds may also be produced by electrolyzing acomposition comprising alkyl magnesium halides and a vinylic halide.This subject matter is not being claimed herein but rather is thesubject of impending application filed on even date. However, it is oneof the unexpected features of the instant invention that improvedresults may he obtained by the electrolysis of the composi- Cit tioncomprising vinylic magnesium halide and alkyl halide over that obtainedby the electrolysis of alkyl magnesium halide and a vinylic halide.Superior yields of the desired product and higher current efiicienciesresult from the process of the instant invention. Again the reason forsuch an improvement by the process of this invention is not understood.

The products of this invention possess considerable utility. Thesecompositions are soluble in hydrocarbons and are valuable as antiknockcompositions for gasolines. The compositions containing the distributedisomers are of particular value. As has been shown this composition maybe produced directly by the process of this invention. The products mayalso be used as monomers in the production of polymers, e.g., for theproduction of copolymers with other vinyl compounds.

Other embodiments of this invention can be made without departing fromthe spirit and scope of this invention which is not limited to thespecific embodiments given herein. For example, tetravinylic leadcompounds may be produced by separating the product of the electrolysisof the vinylic magnesium halide and the alkyl halide.

What is claimed is:

1. An electrolytic process for the production of a mixture oftetraorganolead compounds consisting essentially of a predominant amountof trialkylvinylic lead, dialkyldivinylic lead and alkyltrivinylic leadand small amounts of tetravinylic lead and tetraalkyl lead whichcomprises electrolyzing in an electrolytic cell having a sacrificiallead anode a liquid composition comprising a vinylic Grignard reagentand an alkyl halide, said liquid composition initially having a molratio of alkyl halide to vinylic Grignard reagent of from about 0.1 toabout 10, said vinylic Grignard reagent being at least one compoundrepresented by the formula R C=CHMgX wherein R is at least one radicalselected from the group consisting of H1 CH -CH CH and mixtures thereofand X is a halogen, and said alkyl halide being at least one compoundrepresented by the formula RY wherein R is an alkyl radical selectedfrom the group consisting of alkyl radicals having from 1 to about 8carbon atoms and Y is a halogen.

2. The process of claim 1 further characterized by said liquidcomposition comprising a solvent for said alkyl halide and said vinylicGrignard reagent.

References Cited UNITED STATES PATENTS 3,298,939 1/1967 Linsk 204-592,535,193 12/1950 Calingaert et al. 260-437 3,155,602 11/1964 Linsk etal. 204-59 3,156,716 11/1964 Ramsden et al 260-437 HOWARD S. WILLIAMS,Primary Examiner.

